Q dependence of IMPATT-diode f.m. noise

Measurement of IMPATT-diode-oscillator f.m. noise, for external Q factors ranging between 100 and 10 000, showed that the product of r.m.s. frequency deviation and square root of power output is inversely proportional to the Q factor, in accordance with the Edson formula for f.m. oscillator noise. The excess-noise temperature, varying between 30 and 50dB, rapidly increases with current through the diode. The correlation for f.m. and a.m. noise lies between 0.8 and 1.